1. Field of the Invention
This invention relates to a vehicle suspension system and has particular reference to a third axle attachment for an existing motor vehicle, such as a truck, automobile or the like.
2. Description of the Prior Art
Although motor vehicles are designed to carry a predetermined maximum load, such load is often exceeded. Also, even if a load is within design specifications, it may be located with its center of gravity offset from its optimum position, resulting in overloading of the rear wheels, axle, springs, etc. This not only increases wear and tendency for breakdown of such parts but also can induce dangerous sagging, swaying and bouncing of the vehicle when traversing rough terrain or around curves and corners.
Auxiliary or third axle wheel support devices have been used heretofore, employing additional wheels arranged in tandem with the rear drive wheels of the vehicle to assist in supporting excessive loads. However, those wheel supports of which I am aware are quite expensive and complicated. Also, they generally require extension of the standard chassis frame and/or other modification of the existing vehicle structure such as by drilling holes, welding, etc. Further, such prior devices generally increase the stiffness of the overall spring suspension system throughout its range of deflection thereby resulting in a rough or stiff riding condition when the vehicle is driven with a light load or no load at all. Additionally, such prior devices generally tend to impose a fixed load carrying a capability on the auxiliary wheels so that the amount of load borne by the rear drive wheels may vary as they encounter dips or bumps in the road with consequent tendency to lose traction at times when a greater percent of the load is borne by the auxiliary wheels.